Savannah

Mine disappeared too, it was originally in a lead attached to a fence in a big empty room, but when I went back after being gone for less than one minute, it was gone with the lead laying on the ground

Firstly, Jess I did recreate it in vanilla, as I stated I ran two tests in both vanilla and modded and the rates were pretty much identical (~4k slime/hr). A farm of this design should be running at a rate of at least 10k slime/hr in the environment I built it in. I based it off of a design by Ilmango, but that was before 1.18 and the base design is for one chunk, not three. So my adaptation/design is approximately six times the size, and produces well under half the rate of the base design? Even accounting for the new per-player spawn cap that shouldn't be happening if it's working properly.
Secondly, Thomas, I actually had someone mention that on reddit last night and I confirmed it's likely the issue, but I didn't get around to fixing it then. Also I don't think any of them are despawning, probably just running into a functioning portal and being sent through. I'll post an update once I attempt to fix the nether portal connections.
Edit: so this bug report can be closed as after rebuilding the nether connection & killing chamber it now functions.

You do realize how one obtains said realm name in the list right?

Same exact issue here, it has been working fine on 1.14.30 until today. I have an iPad 7th Gen from Sep 2019. I've rebooted the iPad, offloaded the app and nothing works. 

I see that this is a duplicate, so feel free to link it

thank you

What are mini dumps? 

Also there's a bug with breaking slabs and stairs, where the "breaking" animation plays the bock animation and the parts where there isn't anything just becomes a non-physical grey wall

Yeah if player's aren't supposed to sleep in the nether than villagers shouldn't either, how unusual.

Did you make sure it wasn' accidentally placed into a blast furnace or smoker?

Oh and to be clear I’m on pocket edition if that wasn’t already clear by the IPhone 8 device

Thing is that my game is pocket edition

I’ve had a similar issue where my sister was inmy game and changed my skin to a different skin. For about a week the first thing I would see when I loaded Minecraft was her skin, and I changed it back every time. Don’t know what stopped it though

Actually it’s stuck saying connecting to server when I attempt to connect to any servers

Yeah I find that joining any servers on my IPhone leads to the screen only saying that, It’s probably a problem with Minecraft not loading properly.

Welp just figured out that this also affects my game

The world was created before the update, so that might have something to do with it

Problem is this is quite easy to recreate